Thermoelectric protective unit



y 9, 1956 o. E. ANDRUS THERMOELECTRIC PROTECTIVE UNIT Filed Aug. 31,1955 INVENTOR Orrm E.Anclrus ATTORNEYS.

United States harem THERMOELECTRIC PRQTECTWE Orrin E. Andrus, Milwaukee,Wis, assignor to A;. 0. Smith Corporation, Milwaukee, Wis, a corporationof New York Application August 31, 1953, Serial No. 377,515

11 Claims. (Ci. 219-48) This invention relates to a thermoelectricdevice in combination with the controls of a liquid heating mechanismfor the purpose of insuring the adequate cathodic protection of themetallic surfaces in contact with the liquid being heated or stored.This invention is particularly adapted for protection of a domestic hotwater heater and the like.

An object of the invention is toprovide an automatic shutoif of the mainburner heating the liquid should the cathodic protection becomeinadequate to prevent corrosion of the metal surfaces.

Another object of the invention is to provide a thermoelectric generatorhaving the dual function of serving as a source of current for cathodicprotection and also serving as a source of current for an electricalsafety mechanism with which to control the heat source for the liquid.

Another object of the invention is to provide a thermoelectric generatorunit wherein the casing for the unit may be utilized as one of thethermoelectric elements.

Another object of the invention is toprovide a cathodic protectiondevice which shuts olf the main burner should component parts of thedevice fail.

A further object of the invention is to provide a simply constructed andlow cost unit for insuring cathodic protection of a hot fluid storagetank.

in general, the protective unit comprises a thermoelectric generatorutilized in combination with an anode for cathodic protection of a fluidcontainer and in combination with an electrical device capable ofdiscontinuing the heat supply to the fluid stored in the container forpurposes of warning of inadequacy of cathodic protection and ofminimizing corrosion. For purposes. of illustration, the adaption ofthis device to a domestic hot water heater is described. Thethermoelectric generator, housed in a casing, is heated by such means asa gas flame, a pilot burner, or an electric heating element. It. thesource of heat is reduced for any reason so that the thermoelectricgenerator is not generating a suflicient current for effective ordesired cathodic protection, the current generated and carried to thesafety device hecomes inadequate to energize the electrical device andas a result the heat supply to the water is automatically discontinued.If used with a pilot burner in conjunction with a combustion-typeheater, the electrical device may also shut off the gas supply to thepilot burner to insure maximum. safety. The inability to draw hot. waterfrom the container serves to indicate the probable necessity of repairand relighting of the pilot burner.

Water heater corrosion during a period of shut off of cathodicprotection is substantially arrested by reason of the discontinuance ofheat input. Water is far less corrosive when cold than when hot.Furthermore, dissolved air and carbon dioxide which are necessary tosupport water corrosion are excluded from further entrance into thecontainer if water is not withdrawn by reason of the lack of heatedwater.

Zfidhfiih Patented May 239, 1956 ice In the drawing:

Figure l is a cross-sectional view of the thermoelectric generator unitattached tov the wall of a container and connected. in circuit with ananode and a safety shut oif device;

Fig. 2 is a cross-sectional view of another embodiment of thethermoelectric generator unit;

Pig. 3 isa cross-sectional view of another embodiment of thethermoelectric generator unit;

Fig. 4 is-a cross-sectional view of a fourth embodiment of. theinvention.

Referring particularly to Figure l, the thermoelectric generator. unitcomprises a generally cylindrical casing 1 which is formed from aheat-resistant metal or other suitable material. The casing 1 is formedby deep drawing a blank to provide a one-piece housing having agenerally curved outer end 2. The construction of casing 1 is one pieceso that no welding of the curved outer end 2 need be resorted to inorder to close the outer end of the casing. If welds are employed in theconstruction of casing 1, it is so positioned that the Welds are removedfrom the location where heat is applied, as subsequently described.

Thecasing 1 not only houses the thermoelectric elements, but alsosupports an anode 3 protruding from the casing and extending into thestructure to be protected as disclosed in my copending applicationentitled Thermopile-Anode Structure, Serial No. 365,798, filed July .3,1953. For purposes of illustration, the casing is secured within anopening in the structure to be protected with the open end of the casingextending a suitable distance within the structure. Alhough the casing 1is shown secured to wall 4 by a circumferential weld 5, it may beotherwise secured thereto as by threads.

The open end of easing 1 supports the anode 3 projecting within liquidin the structure. The anode 3 is supported in the casing l as by swagingor clamping'the casing 1 about the anode. To insure a physically strongattachment to the casing i, the anode 3 is annularly recessed, as at 6.A tubular member 7 of neoprene rubber or other suitable insulating andsealing material is disposed between anode 3 and the casing 1. Thetubular member 7 is folded back over. the end of the casing to minimizethe current flow between the anode and the casing 1.

The container Wall is coated with. an insulating lining 8 of vitreousenamel or other suitable material.

The embodiment of the thermoelectric generator unit illustrated inFigure l is composed of a thermopile h and --resist'ant insulatingmaterial is placed between the closed end 2 of the casing 1 and the hotjunctions of the thermopile 9. Similarly, a suitable insulating material12 is disposed between the anode 3 and the cold junctions of thethermopile 9.

In accordance with this invention it is immaterial how thethermopile isconstructed. it will sufi ice to state that the thermopile is suitablyinsulated from the casing or any other metal members with which it mightcome into contact to thereby prevent electrical shorts.

The positive terminal of thermopile 9 is connected to the anode 3 andthe negative terminal is connected to the casing 1. When the hotjunctions of the thermopile are heated, a currentv is generated by thethermopile which flows to the anode, through the liquid within thestructure, to the wall of the structure, and back to the thermopile.

The thermocouple 10 is formed with a conductor 13 and the casing 1 asthe thermoelectric elements. The conductor 13 is welded to the casing 1generally centrally on the inner surface of the curved end 2 thereof toform the hot junction of the thermocouple. Conductor 13 extends throughan aperture 14 in casing 1 and is connected to one side of the relaywinding 15 of electromagnetic relay 16. The casing 1 is connected to theother side of winding 15 by a conductor 17. When the hot junction of thethermocouple is heated, the relay winding 15 is energized and holds acontact 18, carried on an armature 19, in a closed position with acontact 20.

The aperture 14 in the casing is hermetically sealed about the conductor13 in order to prevent the approach of any injurious foreign matter fromthe surrounding atmosphere to the thermopile 9. The sealing of aperture14 in the casing is accomplished by brazing or otherwise securing ametallic tube 21 to the wall of the aperture. The conductor 13 passesthrough the tube 21 and disposed therebetween is powdered magnesiumoxide 22 or other suitable insulating material. The end of the tube 21is sealed by a member 23 of plastic or other suitably pliable materialheld under compressive forces within the end of the tube 21 about theconductor 13. The member 23 is held in the tube 21 by crimping the endof tube 21 inwardly as at 24 over a fiber washer 25 or the like disposedbetween the member 23 and the inwardly crimped portion of the tube. Thisform of seal is disclosed in my copending application entitled, SealedThermopiles, filed April 20, 1953, Serial No. 349,696.

Armature 19 and the contacts 18 and 20 are connected in series in thepower supply circuit of a solenoid operated valve 26. The valve 26 isinserted in the fuel line 27 such that fuel may flow to the main burner,not shown, only when the solenoid 28 is energized.

In addition to the normal function of igniting the main burner, a pilotburner 29 simultaneously heats the thermopile 9 and the thermocouple 1tand thereby creates a flow of current in each when the pilot burner islighted. Although the pilot burner 29 is connected, as diagrammaticallyillustrated, to the fuel supply line following the valve 26, it may beconnected to the fuel line preceding the valve 26. If the pilot burneris connected before the solenoid valve 26, it continues to operate afterthe main burner is extinguished whereas if connected after the valve 26,it is extinguished when the valve closes and the pilot burner unit mustthen be manually re-started.

Although a flame of a pilot burner is illustrated for the operation ofthe thermoelectric generator, it is possible to employ a flame otherthan that of the pilot burner.

The fuel safety shutoff system, as shown, is for purposes ofillustration only and may be replaced by any other suitable electricallycontrolled system; for example, 1) an electromagnetic relay switch toshut oif an electric heating element such as is used in conjunction withelectric water heaters, (2) an electromagnetic relay to operate a smallgas valve which in turn opens and closes the fuel line, or (3) a vacuumtube relay to control the heat source.

The operation of the embodiment of the invention as illustrated inFigure 1 is described as follows:

The pilot burner 29 heats the hot junctions of the thermopile 9 and thethermocouple and thereby generates a current flow in each of them.

The current from the thermopile 9 is employed to cathodically protectthe wall of the structure from corrosion.

The current from the thermocouple 1t energizes the relay winding andholds contact 18 engaged with contact 211 in order to close theenergization circuit for solenoid 28. When energized, the solenoid 28opens the valve 26 and allows fuel to flow to the main burner.

When the flame of pilot burner 29 is extinguished or appreciablydiminished in intensity, the current generated by the thermopile 9 isinadequate to effectively cathodically protect the structure fromcorrosion. If the latter of one end of the casing to one side of therelay 41.

occurs, the current generated by the thermocouple 10 is reduced and therelay winding 15 is de-energized and consequently contact 18 isdisengaged from contact 20. The energization circuit for solenoid 28 isthen open and the valve 26 closes the fuel line 27 with a consequentdiscontinuance of the heating of the liquid within the structure.

The operation of the invention, in general, and the advantages thereofhave been previously described and no further explanation is deemednecessary.

Fig. 2 illustrates a construction of a thermoelectric generator unitwhich does not physically support the anode.

The anode 34) is separately secured to the structure to be protected ofwhich only the wall 31, corresponding to the wall 4 of Figure 1, isshown and insulated therefrom in any suitable manner, such asillustrated and described in my copending application entitled,Self-Sealing Anode Structure, Serial No. 365,797, filed July 3, 1953. Aplug 32 is threaded in the wall 31 with anode 30 extending from the pluginto the liquid within the structure. The anode 30 is insulated from theplug 32 by suitable insulating material 33 disposed therebetween. Anelectrical conductor 34 extends from anode 30 through the plug 32. Apliable sealing and insulating material 35' held under compressiveforces about the conductor 34 seals the unit against leakage.

A thermopile 36 is housed in a hermetically sealed casing 37 with thecold junctions 33 at both ends and hot junctions 39 at the center as setforth in my copending application entitled, Sealed Thermopiles, SerialNo. 349,696, filed April 20, 1953.

The positive lead 41) of the thermopile extends out The negative lead 42of the thermopile is connected to the casing 37 as by weld 43 and thecasing 37 is connected to the wall 31 as by conductor 44-. The relay 41is connected to the anode 311 by conductor 45 to complete a seriescircuit which for purposes of illsutration is shown as follows: Startingwith thermopile 36 the current flows through the relay 41, the anode 36,the fluid in the structure, and the wall 31 of the structure back tothremopile 36.

The relay 41 is connected in a safety circuit, as shown and described inFigure 1, or in any other suitable safety circuit.

The operation of the embodiment of the invention, as shown in Fig. 2, isthe same a described with Figure 1 With the additional safety featurethat if practically any component part of the system fails the heatingmechanism is shut off.

The embodiment of the invention illustrated in Fig. 3 utilizes athermopile with the anode and an electromagnetic winding connected inparallel thereto.

The thermopile 46 is constructed as previously described for Fig. 2. Aconductor 47 is connected to one of the cold junctions of the thremopileto carry a current therefrom to the relay winding 43 of anelectromagnetic gas valve 49. The other side of the relay winding 48 isconnected to the casing as by conductor 50. The condoctor 47 isconnected to the thermopile 46 at any desired junction to carry asuitable current to the relay winding. 48.

For purposes of illustration, a standard electromagnetic gas .valve 49is shown as an alternative safety mechanism for the relay 16 andsolenoid valve 26 of Fig. 1.

The gas valve 49 comprises a chamber 51 with a diaphragm 52 separatingthe chamber into two compartments.

The relay winding 48 is housed within the upper compartment (in thedrawing) and is connected to the thermopile as previously described. Thearmature-53 of relay winding 48 is pivotally supported from the upperwall of the chamber 51.

Positioned to the left of the armature 53 (in the drawarenas-o ing) isan exhaust nozzle 4 terior of the chamber '51.

Positioned to the right of the armature 53 (in the drawing) is a gasinlet nozzle 55 which extends from the chamber 51 and communicates'withthe gas line 56 from the main supply, not shown.

The nozzles 5 and 55 are so positioned with" respect to the armature 53that when the relay winding 48 is energized the gas nozzle 55 is closed;whereas, when the relay winding 48 is de-energized the exhaust nozzle 54is closed. When the one nozzle is closed, the other nozzle is open.

he lower side of the diaphragm 52- carries a valve closure member 57which opens and closes the gas line 56 extending Within the lowercompartment in chamber 51. An outlet pipe 58 carries the gas from thelower chamber to the main burner, not shown, when the gas line 56 isopen.

The operation of the valve is described as follows: The current from thethermopile as energizes the relay winding 43 which closes the gas nozzle55 and opens the exhaust nozzle 5d. The gas flows from the gas line 56forcing the valve member 5'7 up and thereby permits the flow of gas tothe main burner. If the current from the thermopile d6 discontinues oris sufiiciently reduced, the armature 53 is released and the gas nozzle55 opens while the exhaust nozzle 5 closes. Gas then passes through thenozzle 55 and forces the valve member 57 against the valve seat of thegas line 56 and shuts oif the flow of gas to the main burner.

The positive terminal 59 of the thermopile is connected to the anode 60to carry a current thereto. The anode is secured to and insulated fromthe structure Wall 61, as described with respect to Fig. 2. The wall ofthe structure is connected to the thermopile housing 62 as shown byconductor 63.

The embodiments of the invention illustrated in Fig ures l and 3function in the same manner except that the embodiment in Fig. 3 alsodiscontinues the heating of the liquid if the thermopile structurebreaks down.

Other than for the above noted changes, the embodimerit of the inventiondescribed in Fig. 3 is the same as Fig. 2.

Fig. 4 illustrates an embodiment of the invention suitable for use withan electrically heated water heater. This embodiment employs anelectrical heating element to heat the thermoelectric generator.

The thermopile 64 is constructed as previously described with respect toFigs. 2 and 3. The positive terminal 65 is connected to the anode 66'and thenegative terminal is connected to the casing 67 whichis in turnconnected to the structure wall 68.

A thermocouple s9 is housed within the casing 67 and is heated by anelectric heating element 7% which is connected to a suitable source ofheat. The thermocouple 69 is electrically insulated from the thermopile64 and the casing 67.

Thermocouple 69 is connected across the relay winding 71. The relaywinding 71 opens and closes the contacts '72 which are connected to asuitable electric safety system, not shown, to shut off the flow ofelectricity to an electric heating element, not shown, for heating theliquid in the tank. Contacts 72 may, if desired, be so constructed as torequire manual resetting. following the opening of these contacts as aresult of insufiicient heat applied to the thermocouple 69.

Other than for the above noted changes, the embodiment of the inventionillustrated in Fig. 4 is the same as Fig. 2.

The thermocouple 6d may be replaced by a suitable thermopile within thescope of the invention.

The embodiment of the invention in Fig. 4 operates to protect thestructure against corrosion in the same manner as previously describedwith respect to Figure 1.

The above described invention provides a compact which extends to theex- G thermoelectric apparatus for insuring adequate cathodic protectionof a metallic surface in contact with acorosive liquid.

Various modes of carrying out the invention are corrtemplated as withinthe scope of the following claims particularly pointing out anddistinctly claiming the subject matter which is regarded as theinvention.

Various embodiments of the invention may be employed within the scope ofthe following claims.

I claim:

l. A thermoelectric protective apparatus for insuring cathodicprotection of a metallic structure in contact with a heated liquid,which comprises an anode supported in contactwith said liquid, athermoelectric generator having a. positive terminal connected to saidanode and having a negative terminal connected to said structure,electrical insulation disposed between said anode and said structure topermit maintenance of a potential difference therebetw'een by saidthermoelectric generator, a separate source of relatively low heat forenergization of the thermoelectric generator, an electrical heat controldevice connected to the heat source for said liquid, and saidthermoelectric generator being electrically connected to said heatcontrol device to discontinue the heating of said liquid if the currentfrom said thermoelectric generator falls below a predetermined value.

2. A thermoelectric protective apparatus for insuring cathodicprotection of a container for storing a heated liquid, which comprisesan anode in contact with the liquid in the container, electricalinsulating material disposed between said anode and said container topermit maintenance of a potential difference therebetweeu,thermoelectric means electrically connected between said anode and saidcontainer, an electrical heat-control circuit to govern the heating ofsaid liquid, said thermoelectric means connected in the circuit of saidelectrical heat-control circuit to control the current flow therein, ahermetically sealed casing enclosing said thermoelectric means, and asource of heat independent of the main source of heat for the liquid andbeing disposed adjacent said thermoelectric means to cause a generationof current by said thermoelectric means, said construction operating todiscontinue the heating of the fluid within the container when saidthermoelectric means fails to provide a predetermined current flow forcathodic protection.

3'. In a thermoelectric protective device for cathodically protecting avitreous enamel lined container for storing a heated liquid, an anodesupported from the wall of the tank and in contact with said liquid,electrical insulation disposed between said anode and said tank topermit maintenance of a potential therebetween, a thermoelectricgenerator connected between said anode and said container to causecurrent flow from said anode to said container through said liquid, anelectric circuit to govern the heating of said liquid, saidthermoelectric generator connected in saidelectric circuit to controlthe circuit, and an independent source of heat positioned adiacent saidthermoelectric generator to create current flow in said thermoelectricgenerator normally suilicicnt to cathodically protect the containeragainst corrosion, said construction operating to discontinue theheating of the liquid when insuiiicient current flows between said anodeand said container through said liquid to effect adequate cathodicprotection of said container.

4. A thermoelectric protective device for cathodically protecting theinner Wall of a structure for holding a heated liquid, comprising ananode supported within the tank, means to electrically insulate theanode from the tank to limit current flow therebetween to that throughthe liquid in the tank, thermoelectric means electrically connected tothe anode to carry a current thereto, a source of heat adjacent saidthermoelectric means for raising the temperature of the hot junctionsthere of, and control means for controlling the heating of said liquidby the thermoelectric means, said control means connected in seriescircuit with said thermoelectric means and said anode to discontinue theheating of said liquid in the event the current generated by saidthermoelectric means is reduced to a predetermined value.

5. A protective device for protecting a metallic tank against thecorrosive etiects or" a heated liquid within the metallic tank, whichcomprises an anode supported from the wall of said tank and extendingwithin the tank, means to insulate said anode from said tank to confinecurrent flow from the anode to the tank to the flow through the liquidin the tank, a thermopile electrically connected between the anode andthe tank to provide a current flow from said anode to said tank, ametallic casing hermetically housing said thermopile, a conductorelectrically connected to said casing adjacent the hot junctions of thethermopile, said conductor and casing being of dissimilar metals to forma thermocouple, a source of heat positioned adjacent the hot junctionsof said thermopile and said thermocouple, an electric control deviceoperable to discontinue the heating of the liquid, and electricalcircuit connections between said thermocouple and said electric controlto limit the heating of said liquid in response to a predeterminedcurrent generated by said thermocouple.

6. A corrosion-protective apparatus to insure protection of a metallicstructure from corrosive eflects of a heated liquid contained therein,which comprises an anode supported within the structure and insulatedtherefrom in order to limit current flow from said anode to saidstructure to that through the liquid, a thermopile with its positiveterminal connected to the anode and its negative terminal connected tothe structure, electromagnetic means connected to automaticallyinterrupt the heating of the fluid, conductors connecting saidelectromagnetic means to said thermopile in parallel with said anode,and a small source of heat adjacent said thermopile for raising thetemperature of the hot junctions of said thermopile independently of theheating of the liquid.

7. A protective unit for insuring adequate cathodic protection of a tankcontaining a heated liquid, which comprises an anode supported withinthe tank, electrical insulation disposed between said anode and saidtank to limit current flow therebetween to current flowing through theliquid, a thermopile having a positive terminal connected to said anodeand having a negative terminal connected to said tank for the cathodicprotection of the tank, a thermocouple with its hot junctions adjacentthose of said thermopile, a source of heat for simultaneous heating ofthe hot junctions of said thermopile and said thermocouple, an electriccontrol circuit to automatically interrupt the heating of the fluid inthe tank, said thermocouple connected to open said electric controlcircuit and discontinue the heating of the fluid in said tank when thesource of heat is sufliciently reduced, and a casing hermeticallyenclosing said thermopile and said thermocouple.

8. A protective device to prevent corrosion of a tank containing aheated liquid which comprises an anode supported within the tank, meansto electrically insulate the anode from the tank in order to confinecurrent flow from said anode to said tank to that passing through theliquid, a thermopile electrically connected between the anode and thetank wall to provide a potential difference between said anode and saidtank wall, a source of heat for raising the temperature of the hotjunctions of said thermopile, a thermocouple positioned adjacent to andinsulated from said first named thermopile to be heated by said sourceof heat, and an electrically controlled device connected to a heatsupply for said liquid to govern heating of said liquid, saidthermocouple being electrically connected to said device to controloperation of the latter.

9. A protective device to prevent corrosion by a heated liquid in ametallic tank having a pilot burner and a main burner for heating theliquid in the tank, which comprises an anode supported within the tank,means to electrically insulate the anode from the tank to confinecurrent flow therebetween to current flow through the liquid, 3.thermoelectric generator electrically connected between the anode andthe tank to provide a current from the anode to the tank,electromagnetic means operably connected with the main burner toautomatically interrupt the operation of the main burner, saidthermoelectric generator being electrically connected to saidelectromagnetic means to energize the latter, and said thermoelectricgenerator positioned adjacent the pilot burner to be heated thereby.

10. A protective apparatus for the prevention of corrosion by a heatedliquid in a metallic tank having an electric element for heating theliquid in the tank, which comprises an anode supported within the tank,means to electrically insulate said anode from the tank wherebyelectrical conduction from said anode to said tank is limited to thatflowing through the liquid, a thermoelectric generator electricallyconnected between said anode and said tank to provide a current flowfrom the anode to the tank through the liquid, electric control meansoperably connected to the electric heating element for heating saidliquid in the tank to control the heating of the liquid, saidthermoelectric generator being connected in circuit with said electriccontrol means to govern the operation of the latter, and separateelectric heating means to raise the temperature of the hot junctions ofthe thermoelectric generator.

11. In a protective system for the prevention of corrosion by a heatedliquid in a metallic tank, an anode supported within the tank andelectrically insulated therefrom to restrict a current flow from theanode to the tank to that flowing through the liquid, a hermeticallyencased thermopile electrically connected between said anode and saidtank to provide a current flow from the anode to the tank, electriccontrol means connected to govern a source of heat for said liquid,circuit means connecting said thermopile in circuit with said controlmeans, and a separate source of heat for the thermopile providingpredetermined flow of cathodic protection current, said constructionoperating to discontinue the source of heat for said liquid when saidthermopile fails to provide the predetermined current flow.

References Cited in the file of this patent UNITED STATES PATENTS 88,285Farmer Mar. 30, 1869 2,362,259 Findley Nov. 7, 1944 2,443,641 Ray June22, 1948 2,459,123 Bates et al. Jan. 11, 1949 2,649,532 Woodman Aug. 18,1953

